T09 · Insecure Skill Coding Practices
Error
- Location
- lib/config.js:11
- Finding
- Buffer Bearer Credential Can Be Redirected to an Arbitrary or Insecure Endpoint## Vulnerability Details **File Location**: `lib/config.js:11-15` and `lib/buffer-api.js:86-102` **Vulnerability Type**: Unrestricted credential destination and missing transport validation **Risk Level**: High ### Vulnerable Code `lib/config.js:11-15`: ```js export function getConfig() { return { apiKey: process.env.BUFFER_API_KEY, apiUrl: process.env.BUFFER_API_URL || DEFAULT_API_URL, }; } ``` `lib/buffer-api.js:86-102`: ```js constructor(config, httpClient) { this.apiKey = config.apiKey; this.apiUrl = config.apiUrl; this.http = httpClient || axios.create({ baseURL: this.apiUrl, timeout: HTTP_TIMEOUT_MS, headers: { Authorization: `Bearer ${this.apiKey}`, 'Content-Type': 'application/json', }, }); } ``` ### Technical Analysis The application accepts `BUFFER_API_URL` directly from the process environment without validating its scheme, hostname, port, or embedded credentials. The resulting value becomes the Axios base URL, while the Buffer API key is unconditionally attached as a bearer token to every request. Consequently, a malicious or accidentally modified environment configuration can redirect requests and the associated Buffer credential to an arbitrary server. The code also permits an `http://` endpoint, which would expose the token and requested content over an unencrypted connection. Custom API endpoints can be useful for testing, but sending a production credential to an unrestricted destination exceeds the minimum network privileges required for the declared functionality. Normal operation only requires authenticated communication with Buffer's official HTTPS API. ### Attack Path 1. An attacker modifies the user's `.env`, shell environment, deployment configuration, or automation settings. 2. The attacker sets `BUFFER_API_URL` to an attacker-controlled endpoint, such as `https://attacker.example/coll ...[truncated 1231 chars]
- Remediation
- ## Remediation Suggestions 1. Parse the configured endpoint with the standard `URL` class before creating the HTTP client. 2. Require the `https:` scheme and reject cleartext HTTP. 3. Restrict production requests to an explicit allowlist, preferably exactly `api.buffer.com`. 4. Reject URLs containing embedded usernames or passwords, unexpected ports, fragments, or unsupported paths. 5. Use the official endpoint as a fixed production constant, such as `https://api.buffer.com/graphql`, rather than exposing an unrestricted runtime override. 6. If custom endpoints are necessary for tests, require an explicit development-only opt-in and prohibit the use of production credentials. 7. Add tests confirming that non-HTTPS URLs, unexpected hostnames, and malformed URLs are rejected before an authenticated request is made. 8. Consider checking redirect behavior so that authorization headers cannot be forwarded to an untrusted redirect destination.